The present invention relates generally to semiconductor fabrication and, more particularly, to an edge roller assembly, a method for contacting an edge of a substrate, and a transport system for transporting semiconductor wafers to a wafer processing station.
In the fabrication of semiconductor devices, a variety of wafer preparation operations are performed. FIG. 1 is a schematic diagram of a conventional wafer cleaning system 50. The cleaning system 50 includes a load station 10 where a plurality of wafers in a cassette 14 may be inserted into the system for cleaning. Once the wafers are inserted into the load station 10, a wafer 12 may be taken from the cassette 14 and moved into a brush station 16, which includes a first brush box 16a and a second brush box 16b. The wafer 12 is first moved into first brush box 16a, where the wafer is scrubbed in a solution containing specified chemicals and deionized (DI) water. The wafer 12 is then moved into second brush box 16b, where the wafer is again scrubbed in a solution containing specified chemicals and DI water. After the wafer 12 has been scrubbed in brush boxes 16a and 16b, the wafer is moved into a spin, rinse, and dry (SRD) station 20 where DI water is sprayed onto the top and bottom surfaces of the wafer as the wafer is spun. After the wafer 12 has been dried, the wafer is moved from SRD station 20 to an unload station 22.
To achieve the best throughput productivity in wafer cleaning system 50, wafer 12 must be rapidly and efficiently transported from first brush box 16a to second brush box 16b. In comparison with a conveyor system, a robotic xe2x80x9cpick and placexe2x80x9d system is a slow and inefficient way to transport a wafer from the first brush box to the second brush box. Conventional conveyor systems, however, suffer from the drawback that they are capable of transporting wafers only in a horizontal plane. Consequently, these conveyor systems do not interface efficiently with the equipment, e.g., edge clamp devices, that handles a wafer during processing because either the wafer or the track must be moved to obtain the clearance required to process the wafer.
Another problem associated with transporting wafers involves the edge clamp devices. One conventional edge clamp device is a one-piece, custom molded roller wheel. This conventional edge clamp device suffers from two primary disadvantages. First, the molded roller wheel is not reliable because the complicated pattern formed therein causes the wheel to fail prematurely. Second, the molded roller wheel is relatively expensive to manufacture and requires a long lead time.
In view of the foregoing, there is a need for a device that efficiently transports a wafer through a wafer processing station such as, for example, a wafer cleaning system having a first brush box and a second brush box. There also is a need for a reliable and cost effective edge clamp device for use in transporting wafers to a wafer processing station.
Broadly speaking, the present invention fills this need by providing an edge roller assembly that reliably grips the edge of a substrate and is simple and cost effective to manufacture. The present invention also provides a method for contacting an edge of a substrate and a transport system for transporting wafers to a wafer processing station.
In accordance with one aspect of the present invention, an edge roller assembly is provided. The edge roller assembly includes a first grip ring and a second grip ring. The first and second grip rings are held together in an opposing relationship such that outer surfaces thereof define a groove for receiving an edge of a substrate, e.g., a wafer.
In one embodiment, the first and second grip rings are O-rings comprised of a rubber material. The rubber material preferably has a Shore A hardness in a range from about 40 to about 90. Representative rubber materials include VITON rubber, polyurethane rubber, EPDM rubber, and fluoropolymer rubber.
In one embodiment, the edge roller assembly includes a lower clamp plate and an upper clamp plate. In this embodiment, the first and second grip rings are disposed between the lower and upper clamp plates in an opposing relationship such that outer surfaces thereof define a groove for receiving an edge of a substrate. The lower and upper clamp plates may be adjustably fastened together so that the clamping forces the lower and upper clamp plates exert on the first and second grip rings can be controlled.
In one embodiment, the lower clamp plate is in the form of a ring having a surface for receiving the first grip ring and a plurality of holes configured to receive a screw head. In one embodiment, the upper clamp plate includes a surface for receiving the second grip ring, a central throughhole for receiving a drive shaft, a plurality of threaded holes, and a plurality of fingers extending from an upper surface thereof. In one embodiment, the edge roller assembly may include a height adjustment knob rotatably disposed on the fingers extending from the upper surface of the upper clamp plate. The height adjustment knob may have a threaded hole formed therein for receiving a threaded portion of the drive shaft. In one embodiment, the lower clamp plate, the upper clamp plate, and the height adjustment knob are formed of polyethylene terephthalate.
In accordance with another aspect of the present invention, a method for contacting an edge of a substrate is provided. In this method a pair of grip rings are clamped together in an opposing relationship such that outer surfaces thereof define a groove. An edge of a substrate, e.g., a wafer, is then inserted into the groove. In one embodiment, the pair of grip rings is clamped together with a controlled force. In one embodiment, the grip rings are O-rings.
In accordance with yet another aspect of the present invention, a transport system for transporting semiconductor wafers to a wafer processing station is provided. This transport system includes a pair of edge roller assemblies disposed in an opposing relationship. Each of the pair of edge roller assemblies includes first and second grip rings, which may be in the form of O-rings, held together in an opposing relationship such that outer surfaces thereof define a groove for receiving an edge of a wafer. In addition, each of the pair of edge roller assemblies is disposed on a rotatable drive shaft. The transport system is well suited to transport wafers to wafer processing stations at which wafer cleaning operations and wafer buffing operations are performed.
The edge roller assembly of the present invention provides a number of significant advantages. First, the edge roller assembly is simple and cost effective to manufacture because it does not require custom molded parts. Second, the configuration of the edge roller assembly enables the clamping forces exerted on the substrate to be controlled. Third, the grip rings are not subject to premature failure because they do not have any complex patterns formed therein. Fourth, the groove for receiving the edge of the substrate defined by the grip rings provides natural centering action. And fifth, the grip rings can be easily changed, which facilitates the use of diverse substrate contact materials to meet the demands of different applications.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.